[]php replacing text with regular

For help Replace text with regular in PHP
Now there is a text in the page as follows:
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Test text A
[Code=h]aa622ea28638f1e2f9ebc1c845499ed3[/code]
Test text B
[Code=h] D0c93d1fac0843a993431688bd6afd10[/code]
Test text C
[Code=h]0f3d2a4c5bca48f0b9e8e4564defb127[/code]
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As above, how to use regular in PHP to find the above "[Code=h] Start and [/code] End" text, and replaced by another paragraph of text.
Little brother is a novice php, thank you heroes.

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What is the other text like?
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PHP Code

$s =<<< txt Test text a[code=h]aa622ea28638f1e2f9ebc1c845499ed3
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