PHP lesson five

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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