Hướng dẫn str_pad php

(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)

str_pad — Pad a string to a certain length with another string

Description

str_pad(
    string $string,
    int $length,
    string $pad_string = " ",
    int $pad_type = STR_PAD_RIGHT
): string

Parameters

The input string.

If the value of length is negative, less than, or equal to the length of the input string, no padding takes place, and string will be returned.

Note:

The pad_string may be truncated if the required number of padding characters can't be evenly divided by the pad_string's length.

Optional argument pad_type can be STR_PAD_RIGHT, STR_PAD_LEFT, or STR_PAD_BOTH. If pad_type is not specified it is assumed to be STR_PAD_RIGHT.

Return Values

Returns the padded string.

Examples

Example #1 str_pad() example

$input = "Alien";
echo str_pad($input, 10);                      // produces "Alien     "
echo str_pad($input, 10, "-=", STR_PAD_LEFT);  // produces "-=-=-Alien"
echo str_pad($input, 10, "_", STR_PAD_BOTH);   // produces "__Alien___"
echo str_pad($input,  6, "___");               // produces "Alien_"
echo str_pad($input,  3, "*");                 // produces "Alien"
?>

Marjune ¶

7 years ago

since the default pad_type is STR_PAD_RIGHT. using STR_PAD_BOTH were always favor in the right pad if the required number of padding characters can't be evenly divided.

e.g

echo str_pad("input", 10, "pp", STR_PAD_BOTH ); // ppinputppp
echo str_pad("input", 6, "p", STR_PAD_BOTH ); // inputp
echo str_pad("input", 8, "p", STR_PAD_BOTH ); //pinputpp?>

robertwhishaw at gmail dot com ¶

2 years ago

Incrementing or decrementing numbers in PHP is easy with the ++ and -- operators but it can be difficult to set the precision of the numbers. The str_pad() can be useful for concatenating a string to the beginning or end of the incrementing number to simulate a different precision.

Good example, we want to increment 001 to 002, 003, 004:

$numbers = [];

for($i = 1; $i <= 4; $i++){
    $numbers[] = str_pad($i, 3, '0', STR_PAD_LEFT);
}

print_r($numbers);

$numbers[0] => '001',
$numbers[1] => '002',
$numbers[2] => '003',
$numbers[3] => '004',

Bad example, we want to increment 001 to 002, 003, 004 but if we set $i = 001 in the for() loop to start with, 001 will be converted to 1 and the incrementing will return: 1, 2, 3, 4 etc...

$numbers = [];

for($i = 001; $i <= 4; $i++){
    $numbers[] = $i;
}

print_r($numbers);

$numbers[0] => 1,
$numbers[1] => 2,
$numbers[2] => 3,
$numbers[3] => 4,

wes at nospamplsexample dot org ¶

7 years ago

multibyte version:

function mb_str_pad($str, $pad_len, $pad_str = ' ', $dir = STR_PAD_RIGHT, $encoding = NULL)
{
    $encoding = $encoding === NULL ? mb_internal_encoding() : $encoding;
    $padBefore = $dir === STR_PAD_BOTH || $dir === STR_PAD_LEFT;
    $padAfter = $dir === STR_PAD_BOTH || $dir === STR_PAD_RIGHT;
    $pad_len -= mb_strlen($str, $encoding);
    $targetLen = $padBefore && $padAfter ? $pad_len / 2 : $pad_len;
    $strToRepeatLen = mb_strlen($pad_str, $encoding);
    $repeatTimes = ceil($targetLen / $strToRepeatLen);
    $repeatedString = str_repeat($pad_str, max(0, $repeatTimes)); // safe if used with valid utf-8 strings
    $before = $padBefore ? mb_substr($repeatedString, 0, floor($targetLen), $encoding) : '';
    $after = $padAfter ? mb_substr($repeatedString, 0, ceil($targetLen), $encoding) : '';
    return $before . $str . $after;
}
?>

qeremy [atta] gmail [dotta] com ¶

9 years ago

A proper unicode string padder;

mb_internal_encoding('utf-8'); // @importantfunction str_pad_unicode($str, $pad_len, $pad_str = ' ', $dir = STR_PAD_RIGHT) {
    $str_len = mb_strlen($str);
    $pad_str_len = mb_strlen($pad_str);
    if (!$str_len && ($dir == STR_PAD_RIGHT || $dir == STR_PAD_LEFT)) {
        $str_len = 1; // @debug
    }
    if (!$pad_len || !$pad_str_len || $pad_len <= $str_len) {
        return $str;
    }$result = null;
    $repeat = ceil($str_len - $pad_str_len + $pad_len);
    if ($dir == STR_PAD_RIGHT) {
        $result = $str . str_repeat($pad_str, $repeat);
        $result = mb_substr($result, 0, $pad_len);
    } else if ($dir == STR_PAD_LEFT) {
        $result = str_repeat($pad_str, $repeat) . $str;
        $result = mb_substr($result, -$pad_len);
    } else if ($dir == STR_PAD_BOTH) {
        $length = ($pad_len - $str_len) / 2;
        $repeat = ceil($length / $pad_str_len);
        $result = mb_substr(str_repeat($pad_str, $repeat), 0, floor($length))
                    . $str
                       . mb_substr(str_repeat($pad_str, $repeat), 0, ceil($length));
    }

        return

pestilenc at hotmail dot com ¶

20 years ago

For me this worked.
$string = 'help';

#First, str_pad() with unique character.
$string = str_pad($string, 10, "*", STR_PAD_BOTH);
#$string = '***help***';

#Second, str_replace with ' '
$string = str_replace("*", " ", $string);

mcinp ¶

7 years ago

a different, more robust multibyte version of str_pad that works correctly only if $pad_string is non-multibyte string

function my_mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT,$encoding='UTF-8'){
    $mb_diff=mb_strlen($str, $encoding)-strlen($string);       
    return str_pad($input,$pad_length+$mb_diff,$pad_string,$pad_type);
}

bob [at] bobarmadillo [dot] com ¶

19 years ago

In a lot of cases you're better off using str_repeat if you want to use something like   - it repeats the entire string.

Using str_repeat, I wrote a full string pad function that should closely mimic str_pad in every other way:

function full_str_pad($input, $pad_length, $pad_string = '', $pad_type = 0) {
$str = '';
$length = $pad_length - strlen($input);
if ($length > 0) { // str_repeat doesn't like negatives
  if ($pad_type == STR_PAD_RIGHT) { // STR_PAD_RIGHT == 1
   $str = $input.str_repeat($pad_string, $length);
  } elseif ($pad_type == STR_PAD_BOTH) { // STR_PAD_BOTH == 2
   $str = str_repeat($pad_string, floor($length/2));
   $str .= $input;
   $str .= str_repeat($pad_string, ceil($length/2));
  } else { // defaults to STR_PAD_LEFT == 0
   $str = str_repeat($pad_string, $length).$input;
  }
} else { // if $length is negative or zero we don't need to do anything
  $str = $input;
}
return $str;
} $pad_me = "Test String";
echo '|'.full_str_pad($pad_me, 20, ' ')."|\n";
echo '|'.full_str_pad($pad_me, 20, ' ', STR_PAD_RIGHT)."|\n";
echo '|'.full_str_pad($pad_me, 20, ' ', STR_PAD_BOTH)."|\n";
?>

Spudley ¶

15 years ago

Warning: If your string includes non-ascii characters (eg the British pounds sign), str_pad() will treat these as two characters when calculating the padding.

So for example:
str_pad($currency_symbol.$showtottopay,12," ",STR_PAD_LEFT);
?>
will produce a different length string depending on whether $currency_symbol is pounds or dollars.

Hope this helps someone -- it caused me a lot of problems with misaligned columns in my invoices until I worked it out.

neo_selen ¶

2 years ago

you can use str_pad to display an integer with a fixed amount of digits, like that:
0002
0003
...
0100

by just writing

    for ($i=0;$i<10000;$i++){
        echo str_pad($i,4,'0',STR_PAD_LEFT)."\n";
    }
?>

i set 4 digits (see parameter #2), but you can set any fitting your needs.

gene at swipesy dot com ¶

10 years ago

This is how I pad using   :

str_replace(" ", "  ", str_pad($foo, 10, " ", STR_PAD_LEFT))

Seems to work well using two   tags for each character added, at least for my use. YMMV.

Fahad dot Gilani at anu dot edu dot au ¶

19 years ago

Basically, *all* of you guys have a 'long' way of padding text with html tags (which includes  ) You dont even have to do a str_replace... try the following code and this will work with ANY html tag there is out there and you don't have to worry about tag character lengths so on and so forth:
  $text = "This is pretty interesting!";
  $pad_string = " ";

    //Pad text on both sides
  $text = str_pad($text, strlen($text)+(20*strlen($pad_string)), $pad_string, STR_PAD_BOTH);
  print $text." Dont you think?";
?>
Will produce:
          This is pretty interesting!           Dont you think?

Cheers,
Fahad

Kirill Fuchs ¶

5 years ago

sprintf() is not always faster... It certainly scales a lot better then str_pad so when running a benchmark that pads 10k characters,  sprintf will come out on top. But if you benchmarked a more real world scenario, it seems str_pad comes out the clear winner.

$sTime = microtime(true);
$count = 5;
$s = sprintf("%'\n5s", "\n");
$eTime = microtime(true);
echo 'sprintf ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

$sTime = microtime(true);
$s = str_pad("\n", 5, "\n");
$eTime = microtime(true);
echo 'str_pad ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

sprintf ran in 0.015974044799805 milliseconds
str_pad ran in 0.0059604644775391 milliseconds

christian dot reinecke at web dot de ¶

15 years ago

Fills the first argument (mostly a number, f.e. from a loop to display a date or time) with zeroes.

function zerofill($mStretch, $iLength = 2)
{
    $sPrintfString = '%0' . (int)$iLength . 's';
    return sprintf($sPrintfString, $mStretch);
}
?>

sprintf() is indeed faster than str_pad.

gtwizard ¶

5 years ago

sprintf is faster

$sTime = microtime(true);
$s = sprintf("%'-1000000s", '-');
$eTime = microtime(true);
echo 'sprintf ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

$sTime = microtime(true);
$s = str_pad('-', 1000000, '-');
$eTime = microtime(true);
echo 'str_pad ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

//result
sprintf ran in 2.0260810852051 milliseconds
str_pad ran in 26.59797668457 milliseconds

Anonymous ¶

6 years ago

Here is the mcinp's version of mb_str_pad bugfixed:

function mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT,$encoding='UTF-8'){
        $mb_diff=mb_strlen($input, $encoding)-strlen($input);
        return str_pad($input,$pad_length-$mb_diff,$pad_string,$pad_type);
    }
?>

Still working correctly only if $pad_string is non-multibyte string

bxi at apparoat dot nl ¶

14 years ago

In case you want to pad 2 strings together with a character you can use:

function pad_between_strings($string1, $string2, $length, $char = " ") {
    $fill_length = $length - ( strlen($string1) + strlen($string2) );
    return $string1 . str_repeat($char, $fill_length) . $string2;
}
?>

zubfatal ¶

17 years ago

    /**
     * str_pad_html - Pad a string to a certain length with another string.
     * accepts HTML code in param: $strPadString.
     *
     * @name        str_pad_html()
     * @author        Tim Johannessen <>
     * @version        1.0.0
     * @param        string    $strInput    The array to iterate through, all non-numeric values will be skipped.
     * @param        int    $intPadLength    Padding length, must be greater than zero.
     * @param        string    [$strPadString]    String to pad $strInput with (default:  )
     * @param        int        [$intPadType]        STR_PAD_LEFT, STR_PAD_RIGHT (default), STR_PAD_BOTH
     * @return        string    Returns the padded string
    **/
    function str_pad_html($strInput = "", $intPadLength, $strPadString = " ", $intPadType = STR_PAD_RIGHT) {
        if (strlen(trim(strip_tags($strInput))) < intval($intPadLength)) {

                        switch (

$intPadType) {
                 // STR_PAD_LEFT
                case 0:
                    $offsetLeft = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    $offsetRight = 0;
                    break;// STR_PAD_RIGHT
                case 1:
                    $offsetLeft = 0;
                    $offsetRight = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    break;// STR_PAD_BOTH
                case 2:
                    $offsetLeft = intval(($intPadLength - strlen(trim(strip_tags($strInput)))) / 2);
                    $offsetRight = round(($intPadLength - strlen(trim(strip_tags($strInput)))) / 2, 0);
                    break;// STR_PAD_RIGHT
                default:
                    $offsetLeft = 0;
                    $offsetRight = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    break;
            }$strPadded = str_repeat($strPadString, $offsetLeft) . $strInput . str_repeat($strPadString, $offsetRight);
            unset($strInput, $offsetLeft, $offsetRight);

                        return

$strPadded;
        }

                else {
            return

$strInput;
        }
    }?>

matrebatre ¶

13 years ago

Here is a simple function to convert numbers into strings like this:

0 => 0000
1 => 0001
20 => 0020
432 => 0432

function number_pad($number,$n) {
return str_pad((int) $number,$n,"0",STR_PAD_LEFT);
}?>

$n indicates how many characters you want.

private dot email at optusnet dot com dot au ¶

17 years ago

I wrote these 3 functions that live in a library i include in every programme. I find them useful, and the syntax is easy.

$str

= "test";

function

str_pad_right ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + $int;
    $str = str_pad ( $string , $i , $padchar , STR_PAD_RIGHT );
    return $str;
}

    function

str_pad_left ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + $int;
    $str = str_pad ( $string , $i , $padchar , STR_PAD_LEFT );
    return $str;
}

    function

str_pad_both ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + ( $int * 2 );
    $str = str_pad ( $string , $i , $padchar , STR_PAD_BOTH );
    return $str;
}

echo

str_pad_left ( $str , "-" , 3 ); // Produces: ---test
echo str_pad_right ( $str , "-" , 3 ); // Produces: test---
echo str_pad_both ( $str , "-" , 3 ); // Produces: ---test---
?>

Hope this can help someone!

Kari "Haprog" Sderholm ¶

13 years ago

Here's a quick and simple way to make an mb_str_pad function that works when you have correctly set your internal encoding.

I'm not sure how well this works in all possible scenarios but atleast it worked for me using UTF-8 as internal encoding and using this function on strings containing scandinavian characters "åäöÅÄÖ" that are double byte in UTF-8.

function mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT) {
    $diff = strlen($input) - mb_strlen($input);
    return str_pad($input, $pad_length+$diff, $pad_string, $pad_type);
}
?>

NOSPAM dot php at my dot jrklein dot com ¶

2 years ago

str_pad() can provide sufficient "zero padding" when using block ciphers and manual padding with openssl_encrypt() and similar.

The example below will pad the 6 character text "Secret" with two \x00 characters and return 8 characters of data. Substitute your plain text and block size as needed.

$text = "Secret";
$block_size = 8;
$length = ceil(strlen($text) / $block_size) * $block_size;
$data = str_pad($text, $length, "\x00");

mreilly at NOSPAM dot mac dot com ¶

20 years ago

When provided with a string of characters as the pad value, str_pad uses all the characters as fill, and can leave partial strings. (eg. If the pad value is 'ABC' and it needs 5 characters to pad with, it outputs 'ABCAB'.) This is a problem when you want to pad with non-breaking spaces, the code for which is 6 characters long.

This can be resolved by first padding the string with a single character that won't be found in the strings such as * then doing a str_replace of * with  .

Silvio Ginter (silvio dot ginter at gmx dot de) ¶

16 years ago

Hello,

for anyone who needs this, I wrote this extension to str_pad. For details, just look at the comments.

$string

= 'this is a test';
$oldLen = strlen($string);
$direction = STR_PAD_BOTH;
echo $string.'
';
echo str_const_len($string, 101, '#', $direction).'
';
echo $string.'
';
echo str_const_len($string, $oldLen, '#', $direction).'
';
echo $string.'

'."\n"; /*     This function is an extension to str_pad, it manipulates the referenced
    string '$str' and stretches or reduces it to the specified length. It
    returns the number of characters, that were added or stripped. */
function str_const_len(&$str, $len, $char = ' ', $str_pad_const = STR_PAD_RIGHT) {
    $origLen = strlen($str);
    if (strlen($str) < $len) {     /* stretch string */
        $str = str_pad($str, $len, $char, $str_pad_const);
    }
    else {                         /* reduce string */
        switch ($str_pad_const) {
            case STR_PAD_LEFT:
                $str = substr($str, (strlen($str) - $len), $len);
                break;
            case STR_PAD_BOTH:
                $shorten = (int) ((strlen($str) - $len) / 2);
                $str = substr($str, $shorten, $len);
                break;
            default:
                $str = substr($str, 0, $len);
                break;
        }
    }
    return ($len - $origLen);
}
?>

sergey ¶

10 years ago

You can use trim functions for clearpad string:

ltrim("0001230", "0") -> 1230
rtrim("0123000", "0") -> 0123
trim("0012300")     -> 123

pulketo at gmail dot com ¶

5 years ago

// Columnizer: add padding into text columns according maximum column size.
// sample input:
$a='[1515] -> ID=1515 / post_date=2012-06-18 04:48:47 / post_name=review-terminatrix-by-sfam
    [177] -> ID=177 / post_date=2017-05-12 12:12:03 / post_name=review-the-terminator-by-sfam
    [228621100] -> ID=2286 / post_date=2012-06-18 04:48:32 / post_name=terminator-3-rise-of-the-machines-2003';

function columnize($input, $separator=" "){
    $lines = explode("\n", $input);
    foreach ($lines as $k=>$line){
      $r[$k] = explode(" ", trim($line));
    }
    // print_r($r);
    $nc = sizeOf($r[0]);
    // echo $nc;
    for($i=0;$i<$nc;$i++){
      $col[$i] = array_column($r, $i);
      }
    // print_r($col);
    for ($i=0;$i      $maxlen = max(array_map('strlen', $col[$i]));
      $tam[$i]=$maxlen;
      // echo "$i:$maxlen".PHP_EOL;
      $cs[$i]=$maxlen;
    }
    // print_r($cs);
    $o="";
    for ($r=0;$r      for ($c=0;$c        $o.= str_pad($col[$c][$r], $cs[$c]+2, " ", STR_PAD_RIGHT );
      }
      $o .= PHP_EOL;
    }   
    return $o;
  }

echo $columnize($a);
// will output text nicely in columns :)

babak dot asad73 at gmail dot com ¶

2 years ago

how to add some 0 before numbers
for example 5  ===> 005

do something like this:

echo str_pad(5,3,0,STR_PAD_LEFT); // result 005

echo str_pad(4,6,0,STR_PAD_LEFT); // result 000005

Đọc tiếp