There is a buffered output function

ob_start (); / / Open buffer
echo " Hello "; / / output (this time not output characters)
$ temp = ob_get_contents () ;/ / get the current output (currently Hello)
echo 'ob buffer contents:'. $ temp ; / / output the contents just made
ob_end_clean () ;/ / end buffer

Sometimes need to use this way to modify some system packages
For example, the way to use plug
So you want to modify some of the packages can be minimized on the modified amplitude
To achieve the purpose of modifying the content
Click here annotation