如何在PHP中将字符串转换为日期格式？ [重复]

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I am trying to convert a date in string format to date format, here is the example

1. 15Oct15 to 2015-10-15
2. 151015  to 2015-10-15
3. 15102015 to 2015-10-15

Please help me to find a solution.

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You can convert 1. 15Oct15 to 2015-10-15 using date('Y-m-d', strtotime("15Oct15"))

Not sure of other 2