ctype_alpha function to validate alphabetic characters in PHP

$var="abcdef"; // This is alphabetic
//$var="abc=123"; // This is NOT alphabetic
//$var="123"; // This is NOT alphabetic
//$var='xyz12'; // This is NOT alphabetic
//$var='123.56'; // This is NOT alphabetic
//$var=123;  // This is NOT alphabetic

if(ctype_alpha($var)){
	echo " This is alphabetic  ";
}else{ 
	echo " This is NOT alphabetic ";
}

Syntax

bool ctype_alpha(string $input_string)

Returns True or False

By changing the value of $var you can check this function.

By using ctype_alpha function in php we can check or validate alphabetic characters only. Using this function we can check any input coming from insecure ( or any other ) sources. This function is case insensitive so can't differentiate between lower case and upper case alphabetic characters.

We can check user input from a web form for presence of alphabets only, here is the sample code.

if(ctype_alpha($_POST['var'])){
echo " This is alphabetic ";
}else{ echo "this is not alphabetic";}

Checking Array

We can check each element of an array.

$ar=array('abc','as12',123,'ab#1','@12');
foreach ($ar as $var){
if(ctype_alpha($var)){
	echo " $var  is alphabetic  ";
}else{ 
	echo " $var is NOT alphabetic ";
}
echo "<BR>";
}

output

abc is alphabetic
as12 is NOT alphabetic
123 is NOT alphabetic
ab#1 is NOT alphabetic
@12 is NOT alphabetic

Example: Validating a Username

$username = "JohnDoe";
if (ctype_alpha($username)) {
    echo "Valid username";
} else {
    echo "Invalid username";
}

Example: Handling Strings with Spaces

$str = "Hello World";
if (ctype_alpha($str)) {
    echo "Valid string";
} else {
    echo "Invalid string";  // Output: Invalid string
}

Example: Comparing with preg_match()

$str = "JohnDoe";
if (preg_match('/^[a-zA-Z]+$/', $str)) {
    echo "Valid alphabetic string";
} else {
    echo "Invalid string";
}

To check only alphanumeric characters we can use ctype_alnum function.

Subhendu Mohapatra

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ctype_alpha(): Validating only alphabetic characters

Checking Array

Example: Validating a Username

Example: Handling Strings with Spaces

Example: Comparing with preg_match()

Subhendu Mohapatra