php_string.pdf

Types of Strings In PHP
By. Sharon M.

What is String
In PHP, a string is a sequence of characters. It is a data type that can be
used to store text, such as a person's name, a company's name, or a
product description.

Single quotes
This is the simplest way to specify a string. The text is enclosed in single
quotes (the character ').
$str = 'This is a string.';

Double quotes
This is a more versatile way to specify a string. In addition to the
characters that can be enclosed in single quotes, double quotes also
allow you to use escape sequences, such as n for a newline character.
$str = "This is a string with a newline.n"

<?php
$name = 'John';
$age = 30;
// Using single quotes
$singleQuoted = 'My name is $name and I am $age years old.nI am from a single-
quoted string.';
echo "Single-quoted:n$singleQuotedn";
// Using double quotes
$doubleQuoted = "My name is $name and I am $age years old.nI am from a
double-quoted string.";
echo "Double-quoted:n$doubleQuotedn";
?>

Single-quoted:
My name is $name and I am $age years old.nI am from a single-
quoted string.
Double-quoted:
My name is John and I am 30 years old.
I am from a double-quoted string.

Heredoc Syntax
<<< identifier
string
identifier

Heredoc
$str = <<< example
This is a string.
This is the second line.
example;

Heredoc
• Heredoc is a special syntax in PHP that allows you to define a string
that spans multiple lines.
• The heredoc syntax starts with the <<< operator, followed by an
identifier.
• The identifier can be any word or phrase. The string itself follows, and
the identifier is repeated at the end of the string to close the heredoc.

N0w doc - Syntax
<<<'identifier'
string
EOT;

N0w doc - Syntax
$str = <<<'EOT'
This is a nowdoc string.
This is the second line.
EOT;
echo $str;

N0w doc
• Nowdoc is a special syntax in PHP that allows you to define a string
that spans multiple lines, similar to heredoc.
• However, unlike heredoc, nowdoc strings are parsed as single-quoted
strings, so variables and special characters are not interpreted.

Variable Interpolation
• Variable interpolation is a feature in PHP that allows you to insert the
value of a variable into a string.
• This can be useful for creating dynamic content, such as greeting
messages or product descriptions.

$name = 'John Doe';
$message = 'Hello, $name!';
echo $name;
echo $message;

Printing in PHP
1. echo construct
2. print()
3. printf()
4. var_dump()

echo construct
The echo keyword in PHP is used to output text. It is not a function, so
it does not have parentheses.
The arguments to echo are a list of expressions separated by commas.
Expressions can be strings, variables, numbers, or other PHP
constructs.

Example
echo "Hello, world!";
echo $name; // Outputs the value of the variable $name
echo 123; // Outputs the number 123
echo "<h1>This is a heading</h1>"; // Outputs an HTML heading

• PHP, the print statement is used to output text or variables to the
web page.
• It functions similarly to the echo statement but has a subtle
difference:
• print is a language construct rather than a function, and it always
returns a value of 1.

Examples of Print
<?php
print "Hello, World!";
?>
<?php
$message = "Hello, World!";
print $message;
?>

<?php
$result = print "Hello, World!";
echo $result; // This will output "1"
?>

Printf
• printf is a function used for formatted printing.
• It is used to print formatted text to the output, similar to echo or
print, but with more control over the formatting of the output.
• printf is often used when you need to display variables with specific
formatting, such as numbers or dates.

Syntax
printf(format, arg1, arg2, ...)
Example
$name = "John";
$age = 30;
printf("Name: %s, Age: %d", $name, $age);

print_r
• print_r is a built-in function used for displaying information about a
variable or an array in a human-readable format.
• It's particularly useful for debugging and understanding the structure
and contents of complex data structures like arrays and objects.
• Syntax
print_r(variable, return);

Example
$array = array('apple', 'banana', 'cherry');
print_r($array);
o/p
Array
(
[0] => apple
[1] => banana
[2] => cherry
)

var_dump
var_dump is a built-in function used for debugging and inspecting
variables, arrays, objects, or other data structures.
It provides detailed information about a variable's data type, value,
and structure.
var_dump is especially useful when you need to understand the
contents of a variable during development or debugging processes.
var_dump(variable);

Example
$data = 42;
var_dump($data);
int(42)

Exact Comparison
• The === operator in PHP is the identity operator. It checks if two
operands are equal in value and type.
• The == operator is the equality operator. It checks if two operands are
equal in value, but it does not check their type.

Exact Comparison
$string1 = "Hello";
$string2 = "hello";
$number1 = 10;
$number2 = 10.0;
echo $string1 === $string2; // False
echo $string1 == $string2; // True
echo $number1 === $number2; // False
echo $number1 == $number2; // True

Exact Comparison
$string1 = "10";
$number1 = 10;
echo $string1 == $number1; // True

Exact Comparison
This is because the PHP interpreter will automatically convert the string
10 to an integer before comparing it to the number 10.

Approximate Equality
$string = "Hello";
$soundexKey = soundex($string);
echo $soundexKey; // H400

• The metaphone key of a string is a phonetic representation of the
string, based on the English pronunciation of the string.
• The metaphone key is calculated using a set of rules that take into
account the pronunciation of individual letters and letter
combinations.
• The metaphone key is a more accurate representation of the
pronunciation of a string than the Soundex key, because it takes into
account more complex phonetic rules.

$string = "Hello, world!";
$substring = substr($string, 0, 5);
echo $substring; // Output: Hello
// Replace the substring "world" with "Earth"
$substring = substr_replace($string, "Earth", 7);
echo $substring; // Output: Hello, Earth!
// Count the number of occurrences of the substring "world" in a string
$count = substr_count($string, "world");
echo $count; // Output: 1

The substr()
The substr() function extracts a substring from a string. It takes three
parameters:
• The string to extract the substring from.
• The starting position of the substring.
• The length of the substring.
If the third parameter is omitted, the substring will extend to the end of
the string.

substr_replace()
• The substr_replace() function replaces a substring in a string with
another substring. It takes four parameters:
• The string to replace the substring in.
• The replacement string.
• The starting position of the substring to replace.

substr_count()
• The substr_count() function counts the number of occurrences of a
substring in a string. It takes two parameters:
• The string to search for the substring in.
• The substring to search for.

strrev() function
• The strrev() function in PHP is a built-in function that reverses a
string. It takes a single parameter, which is the string to be reversed. It
returns the reversed string as a string.
$reversedString = strrev($string);
echo $reversedString; // !dlrow ,olleH

str_repeat() function
• The str_repeat() function in PHP is a built-in function that repeats a
string a specified number of times. It takes two parameters:
• The string to be repeated.
• The number of times to repeat the string.

Example
$repeatedString = str_repeat($string, 3);
echo $repeatedString; // Hello, world!Hello, world!Hello, world!

str_pad() function
• The str_pad() function in PHP pads a string to a given length. It takes
four parameters:
• The string to be padded.
• The length of the new string.
• The string to use for padding (optional).
• The side of the string to pad (optional).
• If the padding string is not specified, then spaces will be used. If the
side of the string to pad is not specified, then the right side will be
padded.

// Pad the string "hello" to a length of 10, with spaces on the right.
$paddedString = str_pad("hello", 10);
echo $paddedString; // "hello "
// Pad the string "hello" to a length of 10, with asterisks on the left.
$paddedString = str_pad("hello", 10, "*", STR_PAD_LEFT);
echo $paddedString; // "*****hello"
// Pad the string "hello" to a length of 10, with asterisks on both sides.
$paddedString = str_pad("hello", 10, "*", STR_PAD_BOTH);
echo $paddedString; // "***hello**"

explode() function
• The explode() function splits a string into an array, using a specified
delimiter.
• For example, the following code splits the string "hello, world!" into
the array ["hello", "world!"]:

$string = "hello, world!";
$array = explode(",", $string);
print_r($array);
o/p
Array
(
[0] => hello
[1] => world!
)

• The implode() function in PHP joins an array of elements into a string.
It takes two parameters:
• The array of elements to join.
• The separator to use between the elements.
• If the separator is not specified, then a space will be used.
• Here is an example of how to use the implode() function:

Implode () Function
• It creates a string from an array of smaller string.
Syntax :
string implode ( string $glue , array $pieces )
$fruits = array("apple", "banana", "cherry", "date");
$fruitString = implode(", ", $fruits);
echo $fruitString;
o/p - apple, banana, cherry, date

Searching Function
•
The strops function in PHP is a built-in function that finds the position
of the first occurrence of a substring in a string. It is case-sensitive,
meaning that it treats upper-case and lower-case characters
differently.
• The strops function in PHP returns the position of the first occurrence
of a substring in a string, or FALSE if the substring is not found.

$haystack = "Hello, world!";
$needle = "world";
$position = strops($haystack, $needle);
if ($position !== FALSE) {
echo "The substring '$needle' was found at position $position.";
} else {
echo "The substring '$needle' was not found.";
}

•
• The strrstr function in PHP is similar to the strops function, but strrstr
searches for the last occurrence of a substring in a string, while strops
searches for the first occurrence.

$haystack = "Hello, world!";
$needle = "world";
// Return the part of the haystack after the last occurrence of the
substring "world"
$substring = strrstr($haystack, $needle);
echo $substring;

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