- var_dump: documentation ( source)
- str_repeat: documentation ( source)
- preg_replace: documentation ( source)
<?php
$content = '<!--TAG_INI-->' . str_repeat("a\n", 50000) . '<!--TAG_END-->';
$pattern = "/<!--TAG_INI-->.*?<!--TAG_END-->/s";
$content = preg_replace($pattern, 'foo', $content);
var_dump(strlen($content));