[php] How do I escape only single quotes?

I am writing some JavaScript code that uses a string rendered with PHP. How can I escape single quotes (and only single quotes) in my PHP string?

<script type="text/javascript">
    $('#myElement').html('say hello to <?php echo $mystringWithSingleQuotes ?>');
</script>

Here is how I did it. Silly, but simple.

$singlequote = "'";
$picturefile = getProductPicture($id);

echo showPicture('.$singlequote.$picturefile.$singlequote.');

I was working on outputting HTML that called JavaScript code to show a picture...

If you want to escape characters with a \, you have addcslashes(). For example, if you want to escape only single quotes like the question, you can do:

echo addcslashes($value, "'");

And if you want to escape ', ", \, and nul (the byte null), you can use addslashes():

echo addslashes($value);

To replace only single quotes, use this simple statement:

$string = str_replace("'", "\\'", $string);

In some cases, I just convert it into ENTITIES:

                        // i.e.,  $x= ABC\DEFGH'IJKL
$x = str_ireplace("'",  "'", $x);
$x = str_ireplace("\\", "\", $x);
$x = str_ireplace('"',  """, $x);

On the HTML page, the visual output is the same:

ABC\DEFGH'IJKL

However, it is sanitized in source.

I wrote the following function. It replaces the following:

Single quote ['] with a slash and a single quote [\'].

Backslash [\] with two backslashes [\\]

function escapePhpString($target) {
    $replacements = array(
            "'" => '\\\'',
            "\\" => '\\\\'
    );
    return strtr($target, $replacements);
}

You can modify it to add or remove character replacements in the $replacements array. For example, to replace \r\n, it becomes "\r\n" => "\r\n" and "\n" => "\n".

/**
 * With new line replacements too
 */
function escapePhpString($target) {
    $replacements = array(
            "'" => '\\\'',
            "\\" => '\\\\',
            "\r\n" => "\\r\\n",
            "\n" => "\\n"
    );
    return strtr($target, $replacements);
}

The neat feature about strtr is that it will prefer long replacements.

Example, "Cool\r\nFeature" will escape \r\n rather than escaping \n along.

After a long time fighting with this problem, I think I have found a better solution.

The combination of two functions makes it possible to escape a string to use as HTML.

One, to escape double quote if you use the string inside a JavaScript function call; and a second one to escape the single quote, avoiding those simple quotes that go around the argument.

Solution:

mysql_real_escape_string(htmlspecialchars($string))

Solve:

• a PHP line created to call a JavaScript function like

echo 'onclick="javascript_function(\'' . mysql_real_escape_string(htmlspecialchars($string))"

You can use the addcslashes function to get this done like so:

echo addcslashes($text, "'\\");

I am not sure what exactly you are doing with your data, but you could always try:

$string = str_replace("'", "%27", $string);

I use this whenever strings are sent to a database for storage.

%27 is the encoding for the ' character, and it also helps to prevent disruption of GET requests if a single ' character is contained in a string sent to your server. I would replace ' with %27 in both JavaScript and PHP just in case someone tries to manually send some data to your PHP function.

To make it prettier to your end user, just run an inverse replace function for all data you get back from your server and replace all %27 substrings with '.

Happy injection avoiding!

str_replace("'", "\'", $mystringWithSingleQuotes);

Use the native function htmlspecialchars. It will escape from all special character. If you want to escape from a quote specifically, use with ENT_COMPAT or ENT_QUOTES. Here is the example:

$str = "Jane & 'Tarzan'";
echo htmlspecialchars($str, ENT_COMPAT); // Will only convert double quotes
echo "<br>";

echo htmlspecialchars($str, ENT_QUOTES); // Converts double and single quotes
echo "<br>";

echo htmlspecialchars($str, ENT_NOQUOTES); // Does not convert any quotes

The output would be like this:

Jane &amp; 'Tarzan'<br>
Jane &amp; &#039;Tarzan&#039;<br>
Jane &amp; 'Tarzan'

Read more in PHP htmlspecialchars() Function