php - regex to format operators in a expression

Question

I need to get all operators (arithmetic, comparison, logical...) in a string...

((value+10)*10)>=300   ||   (array[key]-20==0&&"foo==bar"!=="")

...and add a single whitespace before and after them (if doesn't already exists)...

((value + 10) * 10) >= 300 || (array[key] - 20 == 0 && "foo==bar" !== "")

...ignoring what is between quotes or single quotes.

Aditional rules:

add space only before pre-in/decrement operators
add space only after post-in/decrement operators

Sounds easy but I can't get how I could do it using regex in PHP. Thanks if someone can help!

I'm trying to do something like $str = preg_replace('(?<=[\w\]\)\s\"\'])\!=(?=[\w\]\)\s\"\'])', ' != ', $str); for every operator, but I don't think it's a good idea.

@MarinoBoscoloNeto - I'd still stick that code in your post just so it demonstrates that you've made the effort. — lintmouse
– lintmouse, Commented Jan 27, 2016 at 19:51

alpha bravo · Accepted Answer · 2016-01-27 20:00:17Z

2

this pattern works with PCRE Engines, which I believe php is

"[^"\r\n]*"(*SKIP)(*F)|\s*([\-\/+*=|<>!&]+)\s*

Demo

answered Jan 27, 2016 at 20:00

alpha bravo

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user4227915 · Accepted Answer · 2016-01-27 20:24:26Z

0

I would use three regexes:

<?php

$str = <<<EOT
(-20+3)
((value+10)*10)>=300   ||   (array[key]-20==0&&"foo==bar"!=="")
EOT;

$str = preg_replace('/("[^"]*"|\([^+=&<>|*\/\\%\w\d-]*|-?\d+|[\w[\]]+|\))/', ' $1 ', $str);
$str = preg_replace('/(?<=\() +| +(?=\))/', '', $str);
$str = preg_replace('/ +/', ' ', $str);

print_r($str);

Check it live here.

answered Jan 27, 2016 at 20:24

user4227915

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