Use PHP regular expression to clear the blank string

We often process data from user input or read from the database. There may be extra spaces or tabs in your string, and press Enter. Storing these extra characters is a waste of space.

You can use the PHP internal function trim () to remove the leading and trailing spaces of the string (). However, we often want to completely clear the blank. You need to clear the white spaces at the beginning and end, change multiple white spaces to one, and use one rule to process other white spaces of the same type.

To do this, you can use the PHP regular expression.

In the following example, additional Whitespace can be removed.

<? Php
$ Str = "This line containstliberal rn use of whitespace. nn ";

// First remove the leading/trailing whitespace
// Remove the start and end spaces.
$ Str = trim ($ str );

// Now remove any doubled-up whitespace
// Remove the blank space crowded with other items
$ Str = preg_replace ('/s (? = S)/', '', $ str );

// Finally, replace any non-space whitespace, with a space
// Finally, remove the non-space blank and replace it with a space.
$ Str = preg_replace ('/[nrt]/', '', $ str );

// Echo out: 'This line contains liberal use of whitespace .'
Echo "<pre >{$ str} </pre> ";
?>


In the previous example, all spaces are removed step by step. First, we use the trim () function to remove the gaps between start and end. Then, we use preg_replace () to remove duplicates. S stands for any whitespace. (? =) Indicates forward lookup. It matches only the characters that are followed by the same character as it. Therefore, this regular expression means: "Any whitespace character followed by the whitespace character. "We will replace it with a blank space, so that we can remove it, leaving the only whitespace character.

Finally, we use another regular expression [nrt] to find any residual line breaks (n), carriage returns (r), or tabs (t ). We use a space to replace these.