PHP: explode but ignore escaped delimiter - php

Question

I have a flatfile database and it is data seperated by delimiters.
I allow people to use the delimiter in their input but I make sure to escape it with a \ beforehand.
The problem is my explode() function still attempts to split the escaped delimiters, so how do I tell it to ignore them?

Answer 1

Use preg_split instead. By using a regex you can match a delimeter only if it is not preceded with a backslash.
Edit:
preg_split('~(?<!\\\)' . preg_quote($delimeter, '~') . '~', $text);

Answer 2

None of the solutions here correctly handle any number of escape characters, or they leave them in the output. Here's an alternative:
function separate($string, $separator = '|', $escape = '\\') {
if (strlen($separator) != 1 || strlen($escape) != 1) {
trigger_error(__FUNCTION__ . ' requires delimiters to be single characters.', E_USER_WARNING);
return;
}
$segments = [];
$string = (string) $string;
do {
$segment = '';
do {
$segment_length = strcspn($string, "$separator$escape");
if ($segment_length) {
$segment .= substr($string, 0, $segment_length);
}
if (strlen($string) <= $segment_length) {
$string = null;
break;
}
if ($escaped = $string[$segment_length] == $escape) {
$segment .= (string) substr($string, ++$segment_length, 1);
}
$string = (string) substr($string, ++$segment_length);
} while ($escaped);
$segments[] = $segment;
} while ($string !== null);
return $segments;
}
This will process a raw string like foo\|ba\r\\|baz| into foo|bar\, baz, and an empty string.
If you want to retain the escape character in the output, you will have to modify the function.
Note: this will have unpredictable behaviour if you're using mb function overloading.

Answer 3

Input Data
key1=val1;key2=val2start\;val2end;key3=val3\\;key4=val4\\\;key5=val5\\\\;key6=val6
REGEX
/(.*?[^\\](\\\\)*?);/
Example
<?php
$data="key1=val1;key2=val2start\\;val2end;key3=val3\\\\;key4=val4\\\\\\;key5=val5\\\\\\\\;key6=val6";
$regex='/(.*?[^\\\\](\\\\\\\\)*?);/';
preg_match_all($regex, $data.';', $matches);
print_r($matches[1]);
Output
Array
(
[0] => key1=val1
[1] => key2=val2start\;val2end
[2] => key3=val3\\
[3] => key4=val4\\\;key5=val5\\\\
[4] => key6=val6
)

Answer 4

You will find this solution more useful than using regex for large strings. I employ a stream to allow usage of fgetcsv, which is optimized for this sort of thing.
<?php
function escaped_explode($string,$delimit,$escape=NULL,$enclosure=NULL,$max_line_length=0){
$r=[];
$stream = fopen('php://memory','r+');
fwrite($stream, $string);
rewind($stream);
while (($data = fgetcsv($stream,$max_line_length,$delimit,$enclosure,$escape)) !== FALSE)
$r=array_merge($r,$data);
fclose($stream);
return $r;
}
?>
Usage:
$pipelined_values = escaped_explode($source,'|','\\');
This is convenient also because you have the option of using enclosures, such as quotes, instead of only escape characters. This is nice if you run into parsing someone's blobs of JSON values, or other syntax, as you can both enclose and escape.
$source= <<<JSON
'{ "key":"val", "n":0}',
'{ "key":"val", "n":1, "name": "French du\'Name" }',
'{ "key":"val", "n":2}'
JSON;
Can be interpreted
<?php
$objects=[];
$raw= escaped_explode($source, ',', '\\', "'");
foreach($raw as $r)
$objects[] = json_decode($r);
?>