Explode on unescaped white space only in PHP - php

Question

I would like to explode this kind of string in PHP:
$foo = "foo.txt da\ code.txt bar.txt";
And I want to explode it to have:
["foo.txt", "da\ code.txt", "bar.txt"]
I know I can use preg_split but I don't see what to put as regular expression.
Could someone help me?

Answer 1

You could match on a positive look behind for any space preceded by alpha characters.
<?php
$foo = "foo.txt da\ code.txt bar.txt";
print_r(preg_split("/(?<=[a-zA-Z])\s/", $foo));
You could also use a negative lookbehind for the general case
<?php
$foo = "foo.txt da\ code.txt bar.txt something.mp3 other# 9asdf";
print_r(preg_split('/(?<!\\\\)\s/', $foo));

Answer 2

Here's a funky, non-regex "parser". All kinds of fun. What was the world like before regular expressions? I mean, it must have been work. ;)
<?php
$foo = "foo.txt da\ code.txt bar.txt";
$foos = array();
$char = 0;
$index = 0;
$lookback = '';
while ($char < strlen($foo)) {
$lookback = $foo{$char-4} . $foo{$char-3} . $foo{$char-2} . $foo{$char-1} . $foo{$char};
if ($lookback == '.txt ') $index++;
$foos[$index] .= $foo{$char++};
}
print_r(array_map('trim', $foos));
?>
http://codepad.org/XMfLemeg

Answer 3

You could use preg_split() but it is slow so if escaped space is your only problem a lot faster would be to do it as simply as:
$array1 = explode(' ', $list);
$array2 = [];
$appendNext = false;
foreach($array1 as $elem)
{
if ($appendNext)
{
array_push($array2, array_pop($array2) . ' ' . $elem);
}
else
{
$array2[] = $elem;
}
$appendNext = (substr($elem, -1) === '\\');
}
var_dump($array2);
If you really want to do it via regex here is a working solution:
print_r(preg_split("/(?<!\\\)\s/", $foo));
http://codepad.org/ngbDaxA3
but it will be slower than above