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

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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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