PHP's str_replace function supports batch replacement of strings through arrays. 1. One-to-one replacement: Set $search and $replace as arrays and replace them one by one in order, such as ['apple','banana'] to ['fruit A','fruit B']; 2. Unified replacement: $search is an array, $replace is a single string, and all matches are replaced with this string, such as ['cat','dog','bird'] to 'animal'; 3. Notes: str_replace is case sensitive, and str_ireplace can ignore case; the replacement order affects the result, and the first match is replaced first, and the subsequent content will not be processed; if the number of $search and $replace is inconsistent, the excess is ignored or replaced with empty.

Sometimes we want to use str_replace to replace multiple keywords with different content, but we don’t want to write a bunch of duplicate replacement statements. At this time, you can directly pass the array in and get it done at once.

PHP's str_replace function supports arrays of search and replacement content, so that the replacement requirements in strings can be processed in batches. For example, if you want to replace "apple" and "banana" in a sentence with "fruit A" and "fruit B" respectively, it will be very convenient to use arrays.

Basic usage: one-to-one replacement

The easiest way is to pass three parameters to str_replace :
The first is the searched array, the second is the replaced array, and the third is the original string.

 $search = ['apple', 'banana'];
$replace = ['Fruit A', 'Fruit B'];
$string = 'I like apple and banana.';

$result = str_replace($search, $replace, $string);

echo $result;
// Output: I like fruit A and fruit B.

What to note here is:

• If $replace is less than $search , the subsequent search terms will be replaced with empty.
• If $replace is more, the excess will be ignored.
• Replacement is in order, with a $search corresponding to a $replace .

Tips for replacing multiple strings simultaneously

If you want to replace multiple strings, and each one needs to be replaced with the same content, you can also pass only one $search array and one string as $replace .

 $search = ['cat', 'dog', 'bird'];
$replace = 'animal';
$string = 'The cat and dog play with the bird.';

$result = str_replace($search, $replace, $string);

echo $result;
// Output: The animal and animal play with the animal.

This writing method is suitable for unified replacement with a certain word, such as filtering sensitive words, unified marking, etc.

Notes: Case and order issues

There are several details that are easily overlooked:

• str_replace is case sensitive. If you want to be case-insensitive, you have to use str_ireplace .
• The order of replacement affects the results. For example, if you replace "apple" first and then "app", then the "app" in "apple" will not be processed again.
• If your replacement content contains the search content itself, it may cause an infinite loop (although PHP will automatically prevent this).

Give a small example to illustrate the impact of sequence:

 $search = ['apple', 'app'];
$replace = ['orange', 'test'];
$string = 'apple is app';

$result = str_replace($search, $replace, $string);
// The result is: orange is test

But if you replace "app" first, it will become:

 $search = ['app', 'apple'];
$replace = ['test', 'orange'];
$string = 'apple is app';

$result = str_replace($search, $replace, $string);
// The result is: orangle is test

Because after "apple" becomes "or app le", "app" has been replaced, so it will not continue to change.

Basically that's it. Batch replacement with arrays is very practical when processing templates, cleaning inputs, and text conversions, but just pay attention to the small details of order and uppercase and uppercase.

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