Creating a string
To declare a string in PHP you can use double quotes ( ” ) or single
quotes ( ‘ ). There are some differences you need to know about using these
two.
If you’re using double-quoted strings variables will be expanded ( processed
). Special characters such as line feed ( \n ) and carriage return ( \r )
are expanded too. However, with single-quoted strings none of those thing
happen. Take a look at the example below to see what I mean.
Note that browsers don’t print newline characters ( \r and \n ) so when
a look at the source and you will see the effect of these newline characters.
<?php
$fruit = ‘jamblang’;
echo “My favourite fruit is $fruit <br>”;
echo ‘I lied, actually I hate $fruit <br>’;
echo “\r\n My first line \r\n and my second line <br>\r\n”;
echo ‘ Though I use \r\n this string is still on one line <br>’;
?>
String Concatenation
To concat two strings you need the dot ( . ) operator so in case you have
a long string and for the sake of readability you have to cut it into two
you can do it just like the example below.
Actually if you need to write a loong string and you want to write it to
multiple lines you don’t need concat the strings. You can do it just like
the second example below where $quote2 is split
into three lines.
<?php
$quote1 = “Never insult Dumbledore ” .
“in front
of me!”;
$quote2 = “Nami,
you are
my nakama!”;
echo $quote1 . “<br>”;
echo $quote2;
?>
String Functions
substr($string, $start, $end) : get a chunk
of $string
<?php
// print ‘12′
echo substr(‘123456789′, 0, 2);
// print ‘56789′
echo substr(‘123456789′, 4);
// print ‘89′
echo substr(‘123456789′, -2);
// print ‘456′
echo substr(‘123456789′, 3, -4);
?>
str_repeat($string, $n) : repeat $string $n
times
For example if you want to print a series of ten asteriks ( * ) you can
do it with a for loop like this :
<?php
for ($i = 0; $i < 10; $i++) {
echo ‘*’;
}
?>
Or you can go the easy way and do it like this :
<?php
echo str_repeat(‘*’, 10);
?>
strrchr($string, $char) : find the last occurence
of the character $char in $string
For example: you want to get the file extension from a file name. You can
use this function in conjunction with substr()
<?php
$ext = substr(strrchr($filename, ‘.’), 1);
?>
What the above code do is get a chunk of $filename
starting from the last dot in $filename
then get the substring of it starting from the second character ( index 1
).
To make things clearer suppose $filename is
‘tutorial.php’. Using strrchr(‘tutorial.php’,
‘.’) yield ‘.php’ and after substr(‘.php’,
1) we get the file extension; ‘php’
trim($string) : remove extra spaces at the
beginning and end of $string
<?php
// print ‘abc def’
echo trim(‘ abc def ‘);
?>
addslashes($string) : adding backslashes before
characters that need to be quoted in $string
This function is usually used on form values before being used for database
queries. You will see this function used a lot in this tutorial so there’s no need to present an example here.
explode($separator, $string) : Split $string
by $separator
This function is commonly used to extract values in a string which are separated
by a a certain separator string. For example, suppose we have some information
stored as comma separated values. To extract each values we ca do it like
shown below
<?php
// extract information from comma separated values
$csv = ‘Uzumaki Naruto,15,Konoha Village’;
$info = explode(‘,’, $csv);
?>
Now, $info is an array with three values :
Array
(
[0] => Uzumaki Naruto
[1] => 15
[2] => Konoha Village
)
We can further process this array like displaying them in a table, etc.
implode($string, $array) : Join the values
of $array using $string
This one do the opposite than the previous function. For example to reverse
back the $info array into a string we can do
it like this :
<?php
$info = array(‘Uzumaki Naruto’, 15, ‘Konoha Village’);
$csv = implode(‘,’, $info);
?>
Another example : Pretend we have an array containing some values and we
want to print them in an ordered list. We can use the implode()
like this :
<?php
// print ordered list of names in array
$names = array(‘Uchiha Sasuke’, ‘Haruno Sakura’, ‘Uzumaki Naruto’, ‘Kakashi’);
echo ‘<ol><li>’ . implode(‘</li><li>’, $names)
. ‘</li></ol>’;
?>
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