How to replace newline character in php regular expression

How to regularly replace newline characters in php: 1. Create a PHP sample file; 2. Replace the newline characters through "preg_replace('//s*/', '', $str);" .

The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer

php How to replace the newline character with regular expression?

Use regular replacement

The code is as follows:

$str = preg_replace('//s*/', '', $str);

Related introduction:

##preg_replace — Execute a Regular expression search and replacement

Instructions

preg_replace(
    string|array $pattern,
    string|array $replacement,
    string|array $subject,
    int $limit = -1,
    int &$count = null
): string|array|null

Search for the part of the subject that matches pattern and replace it with replacement.

Parameters:

pattern

The pattern to search for. Can be a string or an array of strings.

Some PCRE modifiers can be used.

replacement

String or array of strings to use for replacement. If this argument is a string and pattern is an array, then all patterns are replaced with this string. If pattern and replacement are both arrays, each pattern is replaced with the corresponding element in replacement. If there are fewer elements in replacement than in pattern, the extra elements in pattern are replaced with the empty string.

Replacement may contain backreferences \\n or $n, with the latter being syntactically preferred. Each such reference will be replaced by the text captured by the nth capturing subgroup that was matched. n can be 0-99, \\0 and $0 represent the complete pattern matching text. The serial number counting method of capturing subgroups is: the left bracket representing the capturing subgroup is counted from left to right, starting from 1. If you want to use backslashes in replacement, you must use 4 ("\\\\", translation annotation: because this is first a PHP string, after escaping, there are two, and then after passing through the regular expression engine is considered a text backslash).

When working in replacement mode and the backreference needs to be followed by another number (for example: adding an original number immediately after a matching pattern), you cannot use the syntax \\1. Describes backreferences. For example, \\11 will cause preg_replace() to not understand whether you want a \\1 backreference followed by an original 1, or a \\11 backreference followed by nothing. The solution in this case is to use ${1}1. This creates a separate backreference for $1, a separate backreference for source 1.

When using the deprecated e modifier, this function will escape some characters (ie: ', ", \ and NULL) and then perform backreference replacement. When this is done please make sure to After the reference is parsed, there are no syntax errors caused by single quotes or double quotes (for example: 'strlen(\'$1\') strlen("$2")'). Ensure that it conforms to PHP's string syntax and complies with eval syntax. Because in After completing the replacement, the engine will evaluate the resulting string as PHP code using the eval method and return the value as the final string participating in the replacement.

subject

Characters to be searched and replaced String or string array.

If subject is an array, search and replace are performed on each element of subject, and the return value will also be an array.

limit

The maximum number of substitutions per pattern on each subject. The default is -1 (unlimited).

count

If specified, will be filled with the number of completed substitutions .

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