PHP Strings

In PHP, strings are sequences of characters that are used to store and manipulate text. Strings are one of the most commonly used data types, and PHP provides a variety of functions and operators to work with them.

1. Creating Strings

You can create strings in PHP in two ways: using single quotes (') or double quotes (").

a) Single-quoted Strings

• Everything inside the single quotes is treated literally, except for escape sequences like \\ and \'.

$name = 'John Doe';
$sentence = 'This is a string.';

b) Double-quoted Strings

• Double quotes allow for variable interpolation (replacing variables with their values) and special escape sequences.

$name = "John Doe";
$sentence = "Hello, $name!";  // Variable interpolation
echo $sentence;  // Outputs: Hello, John Doe!

• In double-quoted strings, escape sequences such as \n (new line), \t (tab), \$ (dollar sign), \" (double quote) can be used.

$example = "Hello\nWorld";  // Outputs: Hello (new line) World
echo $example;

Note on Variable Interpolation:

Variable interpolation works only inside double-quoted strings, not inside single-quoted strings.

$age = 25;
echo 'Age is $age';  // Outputs: Age is $age (no interpolation)
echo "Age is $age";  // Outputs: Age is 25 (interpolated)

2. String Concatenation

To concatenate (combine) two strings in PHP, you use the dot operator (.).

$firstName = "John";
$lastName = "Doe";
$fullName = $firstName . " " . $lastName;
echo $fullName;  // Outputs: John Doe

You can also use concatenation assignment (.=) to append a string to an existing one.

$message = "Hello";
$message .= " World!";
echo $message;  // Outputs: Hello World!

3. Escape Sequences in Strings

PHP supports special escape sequences for both single and double-quoted strings:

a) In Double-quoted Strings:

• \" – Double quote
• \\ – Backslash
• \n – New line
• \r – Carriage return
• \t – Tab
• \$ – Dollar sign
• \u{X} – Unicode character (where X is the hexadecimal code point)

Example:

$quote = "He said, \"Hello!\"";
echo $quote;  // Outputs: He said, "Hello!"

b) In Single-quoted Strings:

• \\ – Backslash
• \' – Single quote

Example:

$quote = 'It\'s a nice day!';
echo $quote;  // Outputs: It's a nice day!

4. String Length

You can use the strlen() function to get the length of a string (number of characters):

$greeting = "Hello, World!";
echo strlen($greeting);  // Outputs: 13

5. String Comparison

You can compare two strings using comparison operators (==, ===, !=, !==, <, >, etc.).

• ==: Checks if two strings are equal (ignores case).
• ===: Checks if two strings are identical (including case).
• !=: Checks if two strings are not equal.
• !==: Checks if two strings are not identical.

Example:

$str1 = "hello";
$str2 = "HELLO";

echo ($str1 == $str2) ? "Equal" : "Not Equal";  // Outputs: Equal (case-insensitive)
echo ($str1 === $str2) ? "Identical" : "Not Identical";  // Outputs: Not Identical (case-sensitive)

6. String Functions

PHP has many built-in functions for manipulating strings. Here are some of the most commonly used string functions:

• strtoupper(): Converts a string to uppercase.

  $text = "hello";
  echo strtoupper($text);  // Outputs: HELLO
  

• strtolower(): Converts a string to lowercase.

  $text = "HELLO";
  echo strtolower($text);  // Outputs: hello
  

• ucfirst(): Capitalizes the first letter of a string.

  $text = "hello";
  echo ucfirst($text);  // Outputs: Hello
  

• ucwords(): Capitalizes the first letter of each word in a string.

  $text = "hello world";
  echo ucwords($text);  // Outputs: Hello World
  

• substr(): Returns a portion of the string.

  $text = "Hello, World!";
  echo substr($text, 7, 5);  // Outputs: World
  

• strpos(): Finds the position of the first occurrence of a substring in a string.

  $text = "Hello, World!";
  echo strpos($text, "World");  // Outputs: 7
  

• str_replace(): Replaces occurrences of a substring within a string.

  $text = "Hello, World!";
  echo str_replace("World", "PHP", $text);  // Outputs: Hello, PHP!
  

• trim(): Removes whitespace or other predefined characters from both ends of a string.

  $text = "  Hello, World!  ";
  echo trim($text);  // Outputs: Hello, World!
  

• explode(): Splits a string into an array based on a delimiter.

  $text = "apple,banana,orange";
  $fruits = explode(",", $text);
  print_r($fruits);  // Outputs: Array ( [0] => apple [1] => banana [2] => orange )
  

• implode(): Joins elements of an array into a single string.

  $fruits = ["apple", "banana", "orange"];
  echo implode(", ", $fruits);  // Outputs: apple, banana, orange
  

7. Multiline Strings

You can create multiline strings in PHP by using heredoc or nowdoc syntax.

a) Heredoc Syntax:

Heredoc allows you to create a string that spans multiple lines, and variable interpolation works within it.

$name = "John";
$heredoc = <<<EOD
Hello, $name!
This is a multiline string.
EOD;

echo $heredoc;

b) Nowdoc Syntax:

Nowdoc is similar to heredoc but does not support variable interpolation.

$nowdoc = <<<'EOD'
This is a nowdoc string.
Variables like $name won't be replaced.
EOD;

echo $nowdoc;

8. String Padding

PHP provides functions for padding strings with specific characters.

• str_pad(): Pads a string to a certain length with a specified character.

  $text = "Hello";
  echo str_pad($text, 10, "*");  // Outputs: Hello*****
  

Conclusion

• PHP strings are used to handle and manipulate text data.
• Strings can be created using single quotes or double quotes, each with different behaviors for variable interpolation and escape sequences.
• PHP provides a wide range of functions to manipulate strings, including string length, comparison, searching, replacing, and padding.
• You can use heredoc and nowdoc syntax for creating multiline strings in PHP.
• Mastering PHP strings is essential for effective text manipulation and working with dynamic content.