Q:

grep with -f like in PHP

Is there such a function in PHP that does grep -f filename in unix/linux systems.
If there is none, what PHP functions/tools would help in creating a customised method/function for this. Thanks!

A:

Actually IMHO, I'd say it's the following:
$result = preg_grep($pattern, file($path));

See preg_grep­Docs and file­Docs.
If you need to do that (recursively) over a set of files, there is also glob and foreach or the (Recursive)DirectoryIterator or the GlobIterator­Docs and not to forget the RegexIterator­Docs.

Example with SplFileObject and RegexIterator:
$stream = new SplFileObject($file); 
$grepped = new RegexIterator($stream, $pattern); 

foreach ($grepped as $line) {
    echo $line;
}

Output (all lines of $file containing $pattern):
$grepped = new RegexIterator($stream, $pattern); 
foreach ($grepped as $line) {
    echo $line;
}

Demo: https://eval.in/208699

