CODEWITHSUNDEEP
phpregex
jvnbt
jvnbt

Reputation: 2505

Regex to preg_replace '\n' and all other escaped characters in a string?

I have a web app which needs to parse string files from iOS apps. I am trying to find all instances of backslash escapes (\n, \t, \, etc) in a string, and add a span class to them, in PHP. For instance,

"Hello my name is Jim. \nI have \t12\tdogs"

Should become:

"Hello my name is Jim.<span class='b'>\n</span> and I have <span class='b'>\t</span>12<span class='b'>\t</span>dogs"

Unfortunately my regex skills are beyond rusty. I can't figure out how to not just replace the escapes, but add text on each side while retaining them. How can I do this correctly and efficiently? (will potentially be parsing 1000+ strings at a time)

EDIT: to clarify, I want to replace any possible escape characters, not just t and n. So any 2-character set that begins with a '\', including '\\'

Upvotes: 2

Views: 673

Answers (4)

Sidux
Sidux

Reputation: 557

I think this might help you :

if you wanna match non-printable chars and backslash try this :

$newString = preg_replace('/[\s\a\e\\]/', '<span class="b">$1</span>', $oldString);

but if you wanna match all printable alpahnum chars that starts with backslash and the "\x**" format try this :

$newString = preg_replace('/\\[^[:punct:]\s]|\\\\|\\x[a-fA-F0-9]{1,2}/', '<span class="b">$1</span>', $oldString);

this match all chars after backslash expect punctuation chars and chars like \x23, \xAF ...

Upvotes: 0

rtcherry
rtcherry

Reputation: 4880

$newString = preg_replace('/(\\\\\S)/', '<span class="b">$1</span>', $oldString);

One thing to note, when you use \\ in a PHP string, the resulting string actually contains a single \. \\\ and \\\\ will both result in \\.

Example

Upvotes: 0

AbsoluteƵER&#216;
AbsoluteƵER&#216;

Reputation: 7870

From the PHP documentation on Escape Characters:

Single and double quoted PHP strings have special meaning of backslash. Thus if \ has to be matched with a regular expression \\, then "\\\\" or '\\\\' must be used in PHP code.

This is an example with preg_replace. Speed isn't an issue for this script.

$string = 'Hello my name is Jim. \nI have 1\\\2 of \t12\tdogs\r\n';
$pattern = '!(\\\\t|\\\\n|\\\\r|\\\\v|\\\\e|\\\\f|\\\\$|\\\\"|\\\\\\\\|\\\\\\\\\\\\\\\\|\\\\\\\\\\\\)!';
$replacement = "<span class='b'>$1</span>";
$string = preg_replace($pattern,$replacement,$string);
echo "<pre>$string</pre>";

Output

<pre>Hello my name is Jim. <span class='b'>\n</span>I have 1<span class='b'>\\</span>2 of <span class='b'>\t</span>12<span class='b'>\t</span>dogs<span class='b'>\r</span><span class='b'>\n</span></pre>

Upvotes: 1

Bojangles
Bojangles

Reputation: 101473

This is possible without regex, which is good for your speed requirement. A simple str_replace will work:

$string = "Hello my name is Jim. \nI have \t12\tdogs";

$newString = str_replace(
    array("\\t", "\\n"), 
    array("<span class=\"b\">\\t</span>", "<span class=\"b\">\\n</span>"), 
    $string
);

Upvotes: 4

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