Convert special characters to HTML entities

# htmlspecialchars

(PHP 4, PHP 5, PHP 7, PHP 8)

htmlspecialchars — Convert special characters to HTML entities

### Description

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

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) | `&amp;`
`"` (double quote) | `&quot;`, unless `ENT_NOQUOTES` is set
`'` (single quote) | `&#039;` (for `ENT_HTML401`) or `&apos;` (for `ENT_XML1`, `ENT_XHTML` or `ENT_HTML5`), but only when `ENT_QUOTES` is set
`<` (less than) | `&lt;`
`>` (greater than) | `&gt;`

### 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 &#xFFFD; (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 &#xFFFD; (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`.

### See Also

- get_html_translation_table() - Returns the translation table used by htmlspecialchars and htmlentities
- htmlspecialchars_decode() - Convert special HTML entities back to characters
- strip_tags() - Strip HTML and PHP tags from a string
- htmlentities() - Convert all applicable characters to HTML entities
- nl2br() - Inserts HTML line breaks before all newlines in a string

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