str_pad()

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

使用另一个字符串填充字符串为指定长度

说明

该函数返回$input被从左端、右端或者同时两端被填充到制定长度后的结果。如果可选的$pad_string参数没有被指定，$input将被空格字符填充，否则它将被$pad_string填充到指定长度。

参数

输入字符串。

如果$pad_length的值是负数，小于或者等于输入字符串的长度，不会发生任何填充，并会返回$input。

如果填充字符的长度不能被$pad_string整除，那么$pad_string可能会被缩短。$pad_type

可选的$pad_type参数的可能值为STR_PAD_RIGHT，STR_PAD_LEFT或STR_PAD_BOTH。如果没有指定$pad_type，则假定它是STR_PAD_RIGHT。

返回值

返回填充后的字符串。

范例

Example #1str_pad()范例

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

A proper unicode string padder;

Test;

Output;
len 3: ... 
len 3: ... 
len 4: ...A 
len 4: ...Ä 
len 5: A...A 
len 5: Ä...Ä 
len 6: A...AO 
len 6: Ä...ÄÖ 
...

multibyte version:

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);

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);
}

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:

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.

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

sprintf() is indeed faster than str_pad.

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:

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.

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