在给定索引的字符串中插入字符串

You can do anything with regular expressions !

$var = 'myimage.jpg';
$new_var = preg_replace('/\.jpg$/', '.big$0', $var);

我建议大家阅读一下如何编写正则表达式,因为它们在开发中非常有用( here's a starting point ).

substr_replace 要通过用插入替换零长度子字符串来插入字符串,请执行以下操作:

$string = "some-image.jpg";
$insertion = ".big";
$index = 10;

$result = substr_replace($string, $insertion, $index, 0);

length (4)参数):

看这个: http://www.krizka.net/2007/12/29/how-to-insert-a-string-into-another-string-in-php/

$newstring=substr_replace($orig_string, $insert_string, $position, 0);