ob_start — Turn on output buffering
ob_start(callable $callback = null, int $chunk_size = 0, int $flags = PHP_OUTPUT_HANDLER_STDFLAGS): bool
This function will turn output buffering on. While output buffering is active no output is sent from the script (other than headers), instead the output is stored in an internal buffer.
The contents of this internal buffer may be copied into a string variable using ob_get_contents(). To output what is stored in the internal buffer, use ob_end_flush(). Alternatively, ob_end_clean() will silently discard the buffer contents.
ob_start Example
<?php
function callback($buffer)
{
// replace all the apples with oranges
return (str_replace("apples", "oranges", $buffer));
}
ob_start("callback");
?>
<html>
<body>
<p>It's like comparing apples to oranges.</p>
</body>
</html>
<?php
ob_end_flush();
?>
Output
<html>
<body>
<p>It's like comparing oranges to oranges.</p>
</body>
</html>