What is String in PHP ?
They are sequences of characters,
like "Hello World".
A string is a sequence of letters, numbers, special
characters and arithmetic values or combination of all. The simplest way to
create a string is to enclose the string literal (i.e. string characters) in
single quotation marks ('), like this:
$my_string =
'Hello World';
Singly quoted strings are treated
almost literally, whereas doubly quoted strings replace variables with their
values as well as specially interpreting certain character sequences.
You can
also use double quotation marks ("). However, single and double quotation
marks work in different ways. Strings enclosed in single-quotes are treated
almost literally, whereas the strings delimited by the double quotes replaces
variables with the string representations of their values as well as specially
interpreting certain escape sequences.
Strings that are delimited by
double quotes (as in "this") are preprocessed in both the following
two ways by PHP −
·
Certain character sequences beginning with
backslash (\) are replaced with special characters
·
Variable names (starting with $) are replaced
with string representations of their values.
The
escape-sequence replacements are:
- · \n is replaced by the newline character
- · \r is replaced by the carriage-return character
- · \t is replaced by the tab character
- · \$ is replaced by the dollar sign itself ($)
- · \" is replaced by a single double-quote (")
- · \\ is replaced by a single backslash (\)
Example:
<?php
$my_str = 'World';
echo "Hello,
$my_str!<br>";
echo 'Hello, $my_str!<br>';
echo
'<pre>Hello\tWorld!</pre>';
echo
"<pre>Hello\tWorld!</pre>";
echo 'I\'ll be back';
?>
Output:
Hello,
World!
Hello, $my_str!
Hello, $my_str!
Hello\tWorld!
Hello World!
I'll be back
Manipulating PHP Strings
PHP provides many built-in
functions for manipulating strings like calculating the length of a string,
find substrings or characters, replacing part of a string with different
characters, take a string apart, and many others. Here are the examples of some
of these functions.
1)String Concatenation
we concatenate two string variables together, using the dot (.) operator.
Example:
<?php
$string1=”Hello
World”:
$string2=”1234”:
echo $string1.” ”.$string2;
?>
If we look at the code above you
see that we used the concatenation operator two times. This is because we had
to insert a third string.
Between the two string variables
we added a string with a single character, an empty space, to separate the two
variables.
2.Calculating
the Length of a String
The strlen() function is used to calculate the number of characters inside
a string or to find the length of a string.
It also includes the blank spaces inside the string.
Example:
<?php
$my_str = 'Welcome to PHP';
// Calculating and displaying
string length
echo strlen($my_str);
?>
The length of a string is often
used in loops or other functions, when it is important to know when the string
ends. (i.e. in a loop, we would want to stop the loop after the last character
in the string)
3.Using the strpos() function
The strpos() function
is used to search for a string or character within a string.
If a match is found in the string, this function will return
the position of the first match. If no match is found, it will return FALSE.
<?php
echo strpos(“Hello world!”,”world”);
?>
This will produce the following result −6
As you see the position of the string "world" in
our string is position 6. The reason that it is 6, and not 7, is that the first
position in the string is 0, and not 1.
4.Counting Number of Words in a String
The str_word_count() function
counts the number of words in a string.
Example:
<?php
$my_str = 'The quick brown fox
jumps over the lazy dog.';
// Calculating and displaying number of words
echo str_word_count($my_str);
?>
Output:
9
5.Replacing Text within Strings
The str_replace() replaces all occurrences
of the search text within the target string.
<?php
$my_str = 'If the facts do not
fit the theory, change the facts.';
// Display replaced string
echo
str_replace("facts", "truth", $my_str);
?>
Output:
If the truth do
not fit the theory, change the truth.
You can
optionally pass the fourth argument to the str_replace() function
to know how many times the string replacements was performed, like this.
Example:
<?php
$my_str = 'If the facts do not
fit the theory, change the facts.';
// Perform string replacement
str_replace("facts",
"truth", $my_str, $count);
// Display number of replacements performed
echo "The text was replaced
$count times.";
?>
Output:
The text was
replaced 2 times.
6.Reversing a String
The strrev() function reverses a string.
Example:
<?php
$my_str = 'You can do anything,
but not everything.';
// Display reversed string
echo strrev($my_str);
?>
Output:
.gnihtyreve ton
tub ,gnihtyna od nac uoY
7.Using HTML Tags inside print:
we can used HTML tag inside the
string variable –
Example:
<?php
$name=”Sachin <br/> “.”Tendulkar”;
print($name);
?>
Output :
Sachin
Tendulkar