PHP array based on probability returned algorithm

PHP array according to the probability returned algorithm now has a 9 key array: $ arr = array (, 9); I want: 1's return probability is 30% 2's return probability is 20% 3's return probability is 10% 4's return probability is 50% others no matter how such an algorithm calculates it, does this mean? $ ConfigArr PHP array algorithm returned by probability
Now there is a 9-key array:
$ Arr = array (1, 2, 3, 4, 5, 6, 7, 8, 9 );
I hope:
The return probability of 1 is 30%.
The return probability of 2 is 20%.
The return probability of 3 is 10%.
4. The return probability is 50%.
Other
How is this algorithm calculated?


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What does that mean?

$ ConfigArr = array ('20140901', '20160901', '20160901', '20160901 ');

$ Arr = array (1, 2, 3, 4, 5, 6, 7, 8, 9 );
Foreach ($ arr as $ key => $ val)
Echo isset ($ ConfigArr [$ key])? $ Val. 'probability: '. $ ConfigArr [$ key].'
':'';
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Discussion

What does that mean?

$ ConfigArr = array ('20140901', '20160901', '20160901', '20160901 ');

$ Arr = array (1, 2, 3, 4, 5, 6, 7, 8, 9 );
Foreach ($ arr as $ key => $ val)
Echo isset ($ ConfigArr [$ key])? $ Val. 'probability: '. $ ConfigArr [$ key].'
':......

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Discussion

Reference:

What does that mean?

$ ConfigArr = array ('20140901', '20160901', '20160901', '20160901 ');

$ Arr = array (1, 2, 3, 4, 5, 6, 7, 8, 9 );
Foreach ($ arr as $ key => $ val)
Echo isset ($ ConfigArr [$ key])? $ Val. 'probability: '. $ ConfigArr [$ k ......

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Is it true that a number in $ arr = array (, 9); is returned through a function;

The return letter rate is:

The return probability of 1 is 30%.
The return probability of 2 is 20%.
The return probability of 3 is 10%.
4. The return probability is 50%.

!
Is that true?
I have a full idea?
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The numbers are random one by one, for example, 1-random numbers. Returns 1, <= 30, random again, returns 2, <= 20

In short, the number of returned results may exceed 1.
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No .. Soon after I changed my clothes, I was found so quickly ......

Discussion
I wiped it .. The Avatar will also change clothes.


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Agree with amani11.
@ #2 as to whether each number is returned, it is completely an independent event. why should we check whether it is equal to or greater than 100%?