How can PHP developers ensure that a string contains only specific characters like a-z, A-Z, 0-9, ".", "_", and "-" without any spaces?

To ensure that a string contains only specific characters like a-z, A-Z, 0-9, ".", "_", and "-", without any spaces, PHP developers can use a regular expression to validate the string. By using the preg_match function with the appropriate regular expression pattern, developers can check if the string contains only the desired characters. If the string matches the pattern, it means it contains only the specified characters. 

$string = "example_String-123";
if (preg_match('/^[a-zA-Z0-9\.\-_]+$/', $string)) {
    echo "String contains only specified characters.";
} else {
    echo "String contains invalid characters.";
}

Keywords

PHP regular expression preg_match character validation string manipulation

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