PHP Manual: Convert special characters to HTML entities

Description

string htmlspecialchars(
    string $string,
    int $flags = ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML401,
    stringnull $encoding = null,
    bool $double_encode = true
)

Certain characters have special significance in HTML, and should be represented by HTML entities if they are to preserve their meanings. This function returns a string with these conversions made. If you require all input substrings that have associated named entities to be translated, use htmlentities instead.

If the input string passed to this function and the final document share the same character set, this function is sufficient to prepare input for inclusion in most contexts of an HTML document. If, however, the input can represent characters that are not coded in the final document character set and you wish to retain those characters (as numeric or named entities), both this function and htmlentities (which only encodes substrings that have named entity equivalents) may be insufficient. You may have to use mb_encode_numericentity instead.

**Performed translations**
Character	Replacement
`&` (ampersand)	`&`
`"` (double quote)	`"`, unless `ENT_NOQUOTES` is set
`'` (single quote)	`'` (for `ENT_HTML401`) or `'` (for `ENT_XML1`, `ENT_XHTML` or `ENT_HTML5`), but only when `ENT_QUOTES` is set
`<` (less than)	`<`
`>` (greater than)	`>`

Parameters

string

The string being converted.

flags

A bitmask of one or more of the following flags, which specify how to handle quotes, invalid code unit sequences and the used document type. The default is ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML401.

**Available `flags` constants**
Constant Name	Description
`ENT_COMPAT`	Will convert double-quotes and leave single-quotes alone.
`ENT_QUOTES`	Will convert both double and single quotes.
`ENT_NOQUOTES`	Will leave both double and single quotes unconverted.
`ENT_IGNORE`	Silently discard invalid code unit sequences instead of returning an empty string. Using this flag is discouraged as it » may have security implications.
`ENT_SUBSTITUTE`	Replace invalid code unit sequences with a Unicode Replacement Character U+FFFD (UTF-8) or � (otherwise) instead of returning an empty string.
`ENT_DISALLOWED`	Replace invalid code points for the given document type with a Unicode Replacement Character U+FFFD (UTF-8) or � (otherwise) instead of leaving them as is. This may be useful, for instance, to ensure the well-formedness of XML documents with embedded external content.
`ENT_HTML401`	Handle code as HTML 4.01.
`ENT_XML1`	Handle code as XML 1.
`ENT_XHTML`	Handle code as XHTML.
`ENT_HTML5`	Handle code as HTML 5.

encoding

An optional argument defining the encoding used when converting characters.

If omitted, encoding defaults to the value of the default_charset configuration option.

Although this argument is technically optional, you are highly encouraged to specify the correct value for your code if the default_charset configuration option may be set incorrectly for the given input.

For the purposes of this function, the encodings ISO-8859-1, ISO-8859-15, UTF-8, cp866, cp1251, cp1252, and KOI8-R are effectively equivalent, provided the string itself is valid for the encoding, as the characters affected by htmlspecialchars occupy the same positions in all of these encodings.

The following character sets are supported:

**Supported charsets**
Charset	Aliases	Description
ISO-8859-1	ISO8859-1	Western European, Latin-1.
ISO-8859-5	ISO8859-5	Little used cyrillic charset (Latin/Cyrillic).
ISO-8859-15	ISO8859-15	Western European, Latin-9. Adds the Euro sign, French and Finnish letters missing in Latin-1 (ISO-8859-1).
UTF-8		ASCII compatible multi-byte 8-bit Unicode.
cp866	ibm866, 866	DOS-specific Cyrillic charset.
cp1251	Windows-1251, win-1251, 1251	Windows-specific Cyrillic charset.
cp1252	Windows-1252, 1252	Windows specific charset for Western European.
KOI8-R	koi8-ru, koi8r	Russian.
BIG5	950	Traditional Chinese, mainly used in Taiwan.
GB2312	936	Simplified Chinese, national standard character set.
BIG5-HKSCS		Big5 with Hong Kong extensions, Traditional Chinese.
Shift_JIS	SJIS, SJIS-win, cp932, 932	Japanese
EUC-JP	EUCJP, eucJP-win	Japanese
MacRoman		Charset that was used by Mac OS.
`''`		An empty string activates detection from script encoding (Zend multibyte), default_charset and current locale (see nl_langinfo and setlocale), in this order. Not recommended.

Note: Any other character sets are not recognized. The default encoding will be used instead and a warning will be emitted.

double_encode

When double_encode is turned off PHP will not encode existing html entities, the default is to convert everything.

Return Values

The converted string.

If the input string contains an invalid code unit sequence within the given encoding an empty string will be returned, unless either the ENT_IGNORE or ENT_SUBSTITUTE flags are set.

Changelog

Version	Description
8.1.0	`flags` changed from `ENT_COMPAT` to `ENT_QUOTES` \| `ENT_SUBSTITUTE` \| `ENT_HTML401`.

Examples

Example #1 htmlspecialchars example

<?php
$new = htmlspecialchars("<a href='test'>Test</a>", ENT_QUOTES);
echo $new; // &lt;a href=&#039;test&#039;&gt;Test&lt;/a&gt;
?>

Notes

Note:
Note that this function does not translate anything beyond what is listed above. For full entity translation, see htmlentities.

Note:
In case of an ambiguous flags value, the following rules apply:

When neither of ENT_COMPAT, ENT_QUOTES, ENT_NOQUOTES is present, the default is ENT_NOQUOTES.

When more than one of ENT_COMPAT, ENT_QUOTES, ENT_NOQUOTES is present, ENT_QUOTES takes the highest precedence, followed by ENT_COMPAT.

When neither of ENT_HTML401, ENT_HTML5, ENT_XHTML, ENT_XML1 is present, the default is ENT_HTML401.

When more than one of ENT_HTML401, ENT_HTML5, ENT_XHTML, ENT_XML1 is present, ENT_HTML5 takes the highest precedence, followed by ENT_XHTML, ENT_XML1 and ENT_HTML401.

When more than one of ENT_DISALLOWED, ENT_IGNORE, ENT_SUBSTITUTE are present, ENT_IGNORE takes the highest precedence, followed by ENT_SUBSTITUTE.

htmlspecialchars