Writing Date into a field with conditional formatting leads to left alignment

Question

I have a problem with the PhpSpreadsheet. Could you help me, please?! I have to write data into an Excel-file (*.xlsx). Two colums have conditional formatting, like changing the background-color to green, if the word "hello" is written into this field. The fields alignment is set to centered. If PhpSpreadsheet writes "hello" into the conditional formated fields, the Text "hello" leads to left alignment. ... WHY?! Thank you! Bye.