PHP regular expression in action: matching HTML color values

In web development, it is often necessary to use HTML color values ​​to set the style of the page. When processing HTML color values, regular expressions are often needed. This article will introduce how to use PHP regular expressions to match HTML color values.

1. Format of HTML color values ​​

HTML color values ​​have two formats: hexadecimal format and CSS color name format.

1. Hexadecimal format

The HTML color value in hexadecimal format consists of the "#" symbol and six hexadecimal digits, for example: #000000 means black, #FFFFFF means white, #FF0000 means red.

2. CSS color name format

The HTML color value in CSS color name format does not contain the "#" symbol, but directly uses the CSS color name as the color value. For example: red means red, black means black and white means white.

2. Use regular expressions to match HTML color values

1. Match HTML color values ​​in hexadecimal format

Use regular expressions to match hexadecimal format For HTML color values, you can use the following regular expression:

$pattern = '/#([a-f]|[A-F]|[0-9]){6}/';

In this regular expression, the "#" symbol and six hexadecimal digits are used, each of which can be an uppercase or lowercase letter. a-f or A-F, or the numbers 0-9. Use $pattern to match a string. If the string contains a qualified HTML color value, the matching result will be returned.

For example, the following PHP code example demonstrates how to use a regular expression to match a string containing HTML color values:

$string = "这是一个 #000000 的字符串";
$pattern = '/#([a-f]|[A-F]|[0-9]){6}/';
preg_match($pattern, $string, $matches);
print_r($matches);

The above code will output the following results:

Array
(
    [0] => #000000
)

The matching result is an array containing the matched HTML color values.

2. Match HTML color values ​​in CSS color name format

Use regular expressions to match HTML color values ​​in CSS color name format. You can use the following regular expression:

$pattern = '/(red|yellow|blue|green|purple|black|white)/i';

In this regular expression, the CSS color names red, yellow, blue, green, purple, black and white are used. Use $pattern to match a string. If the string contains a qualified HTML color value, the matching result will be returned.

For example, the following PHP code example demonstrates how to use a regular expression to match a string containing an HTML color value in the CSS color name format:

$string = "这是一个 red 的字符串";
$pattern = '/(red|yellow|blue|green|purple|black|white)/i';
preg_match($pattern, $string, $matches);
print_r($matches);

The above code will output the following results:

Array
(
    [0] => red
)

The matching result is an array, which contains the matched HTML color values.

3. Summary

Using PHP regular expressions can easily match HTML color values, especially in web development, which is often used. It should be noted that when using regular expressions, pay attention to the two different formats of HTML color values ​​and use different regular expressions for matching to obtain accurate matching results.

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