语法错误输入字段Html使用php echo [duplicate]

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I' want to show this input via php echo but when i remove the readonly property from an input in the following php sentence:

    <?
echo '<input class="form-control" name="cant-'.$indice.'+'.($t+1).'" id="cant-'.$indice.'+'.($t+1).'" value="'.$cant_guardada.'" readonly="true" ondblclick="this.readOnly='';" onblur="this.readOnly='true';">';
 ?>

And it's throwing this: Error: syntax error, unexpected '';" onblur="this.readOnly='' (T_CONSTANT_ENCAPSED_STRING), expecting ',' or ';'

I know it's a quote related error but I can't seem to find it, can someone help me!

</div>
<?php echo '<input class="form-control" name="cant-'.$indice.'+'.($t+1).'" id="cant-'.$indice.'+'.($t+1).'" value="'.$cant_guardada.'" readonly="true" ondblclick="this.readOnly=\'\';">';  ?>

The single quotes at this.readOnly='' need to be escaped