where to find documentation about the special php exec method using back quotes ? -

i have sample program runs php script exec command using syntax:

echo "do invoke native commmand: ";     `curl "http://localhost/somescript.php`; 

those " ` " sign seems have similar effect regular "exec" command. seems prevent me reading proper response.

now can't find any kind of documentation effect of " ` "

how call ? syntax "exec" or command documented in php docs ?

the backtick operator identical shell_exec(), not exec(). meaning return whole output of cmd string, while exec() returns last line output. (but exec() has additional params whole output and return value of command)

documentation can found in php manual, backtick operator:

php supports 1 execution operator: backticks (``). note these not single-quotes! php attempt execute contents of backticks shell command; output returned (i.e., won't dumped output; can assigned variable). use of backtick operator identical shell_exec().