PHP: Removing Special Characters from Strings

In PHP, removing special characters from strings can be a common task, especially when working with user input or external data. The challenge is to remove all undesired characters without altering essential ones like punctuation or spaces.

To address this issue, a regular expression is commonly used. However, when attempting to remove specific special characters while preserving others, modifications are required to the expression.

Adjusted Regular Expression

The original expression /[^a-zA-Z0-9_ -]/s effectively removes all characters that are not letters, numbers, underscores, spaces, or dashes, but it removes some desirable characters such as parentheses, forward slashes, periods, and ampersands.

To rectify this, we must escape the dot and other special characters that we want to retain. The adjusted expression is as follows:

/[^a-zA-Z0-9_ %\[\]\.\(\)%&-]/s

• Escape the dot with \. to match a literal dot.
• Include additional characters inside square brackets [ ] to match them explicitly.
• Escape other special characters like parentheses (), forward slashes /, and ampersand & to preserve them.

Implementation

To use this regular expression in PHP, replace your original code with the following:

Note: The s modifier in the regular expression signifies that it should work on multiline strings.