A PHP reversible encryption and decryption algorithm

Help a PHP reversible encryption and decryption algorithm
For example algorithm rules:
A=b
B=c
C=d
D=e
......
X=y
Y=z
Z=a
0=1
1=2
2=3
......
8=9
9=0
Letters and numbers are replaced by a certain size letter or number
Example:
Pre-encryption content: 123ABC
Encrypted into: 234def
This way, you can also decrypt the restore by replacing the rules
Please help me with this effect, thank you

Reply to discussion (solution)

$dict = Array (  ' a ' = = ' B ', ' b ' = = ' C ', ' c ' = = '  d ', ' d ' = ' e ', ' 0 ' = ' 1 ', '  1 ' => ; ' 2 ',  ' 2 ' = ' 3 ',  ' 3 ' = ' 4 ', ' echo $t = Strtr (' 123abc ', $dict), Php_eol;echo strtr ($t, Array_flip ($dict));

234bcd123abc

Thank you very much, it turned out to be these two functions

