In this PHP tutorial, you shall learn how to check if given string contains only uppercase letters using ctype_upper() function, with example programs.
PHP – Check if string contains only uppercase letters
To check if a string contains only uppercase letters in PHP, call ctype_upper() function and pass given string as argument.
The ctype_upper() function returns a boolean value representing of the situation: if the string contains only uppercase characters.
Syntax
The syntax to check if string str contains only uppercase letters is
ctype_upper($str)
The above expression returns a boolean value of true if the string $str contains only uppercase characters, or false otherwise.
Examples
1. Positive Scenario – String contains only uppercase
In this example, we take a string in str such that it contains only uppercase characters. For the given value of string, ctype_upper() returns true and if-block executes.
PHP Program
<?php
$str = 'APPLE';
if ( ctype_upper($str) ) {
echo 'string contains only uppercase';
} else {
echo 'string does not contain only uppercase';
}
?> Output
2. Negative Scenario – String contains lowercase also
In this example, we take a string in str such that it contains some lowercase letters also, along with uppercase letters. For the given value of string, ctype_upper() returns false and else-block executes.
PHP Program
<?php
$str = 'APPle';
if ( ctype_upper($str) ) {
echo 'string contains only uppercase';
} else {
echo 'string does not contain only uppercase';
}
?> Output
3. Negative Scenario – String contains digits also
In this example, we take a string in str such that it contains digits also, along with uppercase letters. For the given value of string, ctype_upper() returns false and else-block executes.
PHP Program
<?php
$str = 'APPLE123';
if ( ctype_upper($str) ) {
echo 'string contains only uppercase';
} else {
echo 'string does not contain only uppercase';
}
?> Output
Conclusion
In this PHP Tutorial, we learned how to check if given string contains only uppercase characters, using ctype_upper() function, with the help of examples.