This article discusses some techniques of manipulating data in an array. To keep it simple, let's start by looking how we can remove quotes from a variable. To remove a character, we can replace it with nothing using str_replace() function.

$a = "'pineapple'";
$b = '"guava"';
print "$a $b\n";
$a = str_replace("'","",$a);
$b = str_replace('"','',$b);
print "$a $b\n";

This results in:

'pineapple' "guava"
pineapple guava

Suppose we need to be perform this operation on every element of the array. The logical place to start would be to use a foreach loop.

print "original\n";
$fruits = array("'apple'","'banana'","'nectar'");
print_r($fruits);

print "Using foreach\n";
foreach ($fruits as $fruit) { $fruit = str_replace("'","",$fruit); }
print_r($fruits);

Unfortunately this does not work as the variable $fruit is temporary variable which holds a copy of the given element. Modifying the value of this$fruit does not modify the value of the desired element in the array.

original
Array
(
    [0] => 'apple'
    [1] => 'banana'
    [2] => 'nectar'
)
Using foreach
Array
(
    [0] => 'apple'
    [1] => 'banana'
    [2] => 'nectar'
)

Let's try this with a for loop.

print "original\n";
$fruits = array("'apple'","'banana'","'nectar'");
print_r($fruits);

print "Using for loop\n";
for ($i = 0; $i < count($fruits); $i++) {
  $fruits[$i] = str_replace("'","",$fruits[$i]);
}
print_r($fruits);

Pretty self-explanatory. Loop through the array, extract each element, remove quotes and replace the original element in the array with this one.

original
Array
(
    [0] => 'apple'
    [1] => 'banana'
    [2] => 'nectar'
)
Using for loop
Array
(
    [0] => apple
    [1] => banana
    [2] => nectar
)

Very often we are interested in performing more complex manipulations than simply removing codes. In such cases, it is a good idea to delegate the work to a function.

function strip_single_quotes($value)
{
  return str_replace("'","",$value);
}
print "original\n";
$fruits = array("'apple'","'banana'","'nectar'");
print_r($fruits);

print "Using for loop by value\n";
for ($i = 0; $i < count($fruits); $i++) {
  $fruits[$i] = strip_single_quotes($fruits[$i]);
}
print_r($fruits);

strip_single_quotes() is called by value, meaning that strip_single_quotes() receives a copy of the the array element. strip_single_quotes() removes quotes from this copy and returns the modified copy. This copy then replaces the array element. The result of this program:

original
Array
(
    [0] => 'apple'
    [1] => 'banana'
    [2] => 'nectar'
)
Using for loop by value
Array
(
    [0] => apple
    [1] => banana
    [2] => nectar
)

Another way to accomplish the same is by sending a reference rather than a copy to the function.

function remove_single_quotes(&$value)
{
  $value = str_replace("'","",$value);
}

print "original\n";
$fruits = array("'apple'","'banana'","'nectar'");
print_r($fruits);

print "Using for loop by reference\n";
for ($i = 0; $i < count($fruits); $i++) {
  remove_single_quotes($fruits[$i]);
}
print_r($fruits);

Here we send a reference (address of) the array element. Note the &$ in remove_single_quotes(). As remove_single_quotes() operates on the original element, there is no need to return a value. The output:

original
Array
(
    [0] => 'apple'
    [1] => 'banana'
    [2] => 'nectar'
)
Using for loop by reference
Array
(
    [0] => apple
    [1] => banana
    [2] => nectar
)

A nicer way to accomplish the same is by using array_walk() instead of a loop. array_walk() iterates through an array apply a function to each element of the array.

function remove_single_quotes(&$value)
{
  $value = str_replace("'","",$value);
}

print "original\n";
$fruits = array("'apple'","'banana'","'nectar'");
print_r($fruits);

print "Using array_walk\n";
array_walk($fruits,'remove_single_quotes');
print_r($fruits);

The output:

original
Array
(
    [0] => 'apple'
    [1] => 'banana'
    [2] => 'nectar'
)
Using array_walk
Array
(
    [0] => apple
    [1] => banana
    [2] => nectar
)

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