PHP - Check if string contains only lowercase letters

In this PHP tutorial, you shall learn how to check if given string contains only lowercase letters using ctype_lower() function, with example programs.

PHP – Check if string contains only lowercase letters

To check if a string contains only lowercase letters in PHP, call ctype_lower() function and pass given string as argument.

The ctype_lower() function returns a boolean value representing if the string contains only lowercase characters.

Syntax

The syntax to check if string str contains only lowercase letters is

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ctype_lower($str)

The above expression returns a boolean value of true if the string $str contains only lowercase characters, or false otherwise.

Examples

1. Positive Scenario – String contains only lowercase

In this example, we take a string in str such that it contains only lowercase characters. For the given value of string, ctype_lower() returns true and if-block executes.

PHP Program

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<?php
  $str = 'apple';
  if ( ctype_lower($str) ) {
    echo 'string contains only lowercase';
  } else {
    echo 'string does not contain only lowercase';
  }
?>

Output

PHP - Check if string contains only lowercase letters - Example 1

2. Negative Scenario – String contains uppercase also

In this example, we take a string in str such that it contains some uppercase letters along with lowercase letters. For the given value of string, ctype_lower() returns false and else-block executes.

PHP Program

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<?php
  $str = 'Apple';
  if ( ctype_lower($str) ) {
    echo 'string contains only lowercase';
  } else {
    echo 'string does not contain only lowercase';
  }
?>

Output

PHP - Check if string contains only lowercase letters - Example 2

3. Negative Scenario – String contains digits also

In this example, we take a string in str such that it contains some digits along with lowercase letters. For the given value of string, ctype_lower() returns false and else-block executes.

PHP Program

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<?php
  $str = 'apple123';
  if ( ctype_lower($str) ) {
    echo 'string contains only lowercase';
  } else {
    echo 'string does not contain only lowercase';
  }
?>

Output

PHP - Check if string contains only lowercase letters - Example 3

Conclusion

In this PHP Tutorial, we learned how to check if given string contains only lowercase characters, using ctype_lower() function, with the help of examples.

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